# Release the backend instances of the traditional load balancer - ReleaseBackend

## Overview

Release backend resource instances from CLB's VServer



 > ℹ️ When VServer is at Layer 7, the backend instance must be removed from the forwarding rules before it can be released. BackendId corresponds to the BackendId returned by AllocateBackend or the BackendId in ULBBackendSet returned by DescribeULB/DescribeVServer, which is the node Id of the traditional load balancing service.


## Definition

### Public Parameters

| Parameter Name | Type | Description Information | Required |
|:---|:---|:---|:---|
| **Action**     | string  | Corresponding API command name, the current API is `ReleaseBackend`.                      | **Yes** |
| **PublicKey**  | string  | The user's public key can be obtained from [Console](https://console.scloudsg.com/uaccount/api_manage)                                             | **Yes** |
| **Signature**  | string  | User signature generated based on public key and API command, see [Signature Algorithm](/docs/api/summary/signature.md)  | **Yes** |

### Request Parameters

| Parameter Name | Type | Description Information | Required |
|:---|:---|:---|:---|
| **Region** | string | Region. See [List of Regions and Availability Zones](/docs/api/summary/regionlist) |**Yes**|
| **ProjectId** | string | Project ID. If not filled in, the default project is used, sub-accounts must be filled in. Please refer to the [GetProjectList interface](/docs/api/summary/get_project_list). |**Yes**|
| **ULBId** | string | ID of the traditional load balancing instance |**Yes**|
| **BackendId** | string | ID of the backend resource instance (CLB backend ID, not the resource's own ID) |**Yes**|

### Response Field

| Field Name | Type | Description Information | Required |
|:---|:---|:---|:---|
| **RetCode** | int | Return status code. If it is 0, it means successful return. If it is not 0, it means failure. |**Yes**|
| **Action** | string | Operation command name. |**Yes**|
| **Message** | string | Returns an error message, providing detailed description when `RetCode` is non-zero. |No|




## Example

### Request Example
    
```
https://api.scloudsg.com/?Action=ReleaseBackend
&Region=cn-bj2
&ProjectId=project-XXXX
&ULBId=ulb-XXXX
&BackendId=backend-XXXX
```

### Response Example
    
```json
{
  "Action": "ReleaseBackendResponse",
  "RetCode": 0
}
```